High vacuum pump



Jan. 23, 1968 s. KAINER HIGH VACUUM PUMP Filed April 25, 1966 S: (b u E. w

INVENTOR.

United States Patent f 3,365,119 HIGH VACUUM PUMP Selig Kainer, New York, N.Y., assignor to International Telephone and Telegraph Corporation, Nutley, N.J., a corporation of Maryland Filed Apr. 25, 1966, Ser. No. 545,042 Claims. (Cl. 230-69) ABSTRACT OF THE DHSCLOSURE The combination of an ion pump and mercury diffusion pump wherein, with the same physical apparatus, two types of pumping actions are simultaneously performed, entrapment by condensing vapors and embedment in a target.

This invention relates generally to apparatus for a high vacuum pump, and more particularly to a combination of an ion pump and diffusion pump.

Of the vacuum pumps available heretofore, two diflerent types have found extensive use. First of these types is a diffusion pump. The diffusion process in ordinary mercury or oil diffusion pumps consists of heating the pumping fluid until a suflicient high vapor pressure is obtained. This vapor rises to the top of the reservoir and into a condensing chamber as a jet, entrapping molecules of the gas to be pumped prior to condensing and being pumped along by a forepump. The cycle is repeated continuously.

The second type of vacuum pump in general use for producing a vacuum is of the ion vacuum pump type. In this type of vacuum pump, there is generally located within the evacuating envelope a filament-like structure which will produce electrons, and at least one ion collector element. The gas molecules diffuse from the chamber to be evacuated into the envelope where they are subjected to bombardment by the electrons produced by the filament arrangement or high voltage gas discharge. This electron bombardment results in positively charged ions being produced, these ions are then attracted to a cathode where embed-ment occurs. Further burial is accomplished by sputtering from the cathode to produce finely divided metal which aids the vacuum process thru chemical reaction, absorption, and burial. Disadvantages are that heavy hydrocarbons poison the cathode and rare gases are not permanently removed from the system.

According to the broader aspects of this invention, the same physical apparatus may simultaneously perform the two pumping actions described above, namely, entrapment by condensing vapors and embedment in a target. This permits certain advantages over using either a diffusion pump or an ion pump alone, because the affective pumping of the diffusion pump part as used in combination is increased, and the back-streaming of the pumping fluid molecules will produce controllable conditions in the discharge space thru cold trapping. And unlike the ion pump where the gases accumulate in the cathode, the target presented to the ionized molecules according to this combination pump is constantly cleaned as the embedded gases are pumped out by a fore-pump. Unlike ion pumps, there is no special problem in using this combination apparatus in connection with rare gases.

Another advantage of this combination diffusion and ion :pump not exhibited by any pump heretofore, is a fact that thesame physical apparatus may be operated in three ways, as a diffusion pump, as an ionic pump, and

3,365,119 Patented Jan. 23, 1968 as a combination diffusion and ionic punip in which the optimum operating point is selected according to the needs of the particular system to be evacuated.

It is therefore an object of the apparatus according to this invention to act as a diffusion pump, in which the pumping action of the condensing vapor is increased by ionic current which increases the pump rate of the system as well as reduces back streaming.

Another object of the apparatus according to this invention is to produce a vacuum as an ionic pump where no use is made of the condensing vapor, but a film of pumping fluid captures the molecules by embedrnent.

A principal object of the apparatus according to the present invention is to produce a vacuum by the combinations and simultaneous operation of two pumping actions, entrapment and embedrnent, where the optimum operating point is selected according to the needs of the system to be evacuated.

According to the broader aspects of this invention, a feature is to produce a high vacuum by heating of a pumping fluid until a sufficiently high pressure is obtained, and the vapor produced to entrap molecules of the gases to be pumped in a condensing chamber, these entrapped molecules to be pumped out along the forepump. And at the same time, to accelerate ionized gas molecules towards the same condensing chamber to be embedded in a film of the pumping fluid. This film constantly presents a clean target to the ionized gas molecules which are embedded in the film pump and removed by the forepump.

The above mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in connection with the accompanying drawing, in which:

The single figure of the drawing is a schematic diagram of an embodiment of the apparatus according to the principles of this invention.

Referring now to the drawing, the simultaneous operation of the two pumping actions which will be described. Pumping fluid 1, such as ordinary mercury, is suitably heated by a heater 2 to produce sufliciently high vapor pressure in container 3. This vapor rises to the top of container 3 and is carried by conduit 4 to condensing chamber 5, surrounded by cooling coils 6 to sufliciently cool the vapor to pumping fluid 1 which has entrapped the molecules of gas entering condensing chamber 5 by means of inlet 7 which is connected to the system to be evacuated. As the entrapped gas molecules and the condensing vapors move towards the bottom portion of condensing chamber 5, the entrapped gases are pumped by means of a forepump connected to outlet 8. Since this cycle repeats continuously, the condensed vapor forms a secondary reservoir at the bottom of condensing chamber 5 which is connected by means of conduit 9 to return the pumping fluid back to the primary reservoir in chamber 3.

Operation of the second pumping action, as an ionic pump, will now be discussed. Connected to inlet 7 is an ion chamber 10 having an anode 11, an ionizer 12, which may be a heated tungsten wire, an auxiliary cathode 13, and an ion chamber 10 is connected by conduit 14 to condensing chamber 5. A second condensing coil 15 surrounding conduit 4 condenses a desired portion of the vapor being transferred in conduit 4 to produce a continuously flowing film 16 along the Wall of condensing chamber 5. The pumping fluid film flows down the wall of condensing chamber 5 and over primary cathode 17. The electrons produced by ionizer 12 move in a circular pattern under the influence of magnet 18 to ionize the gas molecules entering inlet 7 and also the back streaming pumping fluid molecules which enter chamber 10. The ionized gas molecules then under the influence of the high electric fields produced by anode 11, auxiliary cathode 13, and primary cathode 17 are accelerated into the condensing chamber 5, and due to the high energy embed themselves in the flowing film of the pumping fluid which covers primary cathode 17, and the film carries the molecules to the bottom of the condensing chamber 5 to be pumped out by the forepump. The film of the pumping fluid over the primary cathode 17 presents a continually clean target for the accelerated ionized molecules. The film is then collected at the bottom of condensing chamber 5 and transferred by conduit 9 to the bottom of chamber 3 and recycled.

This pump has some substantial advantages over high vacuum pumps in current use, in that control of cooling coils 15 and control of cooling coils 6 allows one to operate this pump at an optimum point depending on the system to be evaporated. For example, should one desire to operate the apparatus as a diffusion pump alone, then cooling coil 15 need not be activated to condense the vapor produced in chamber 3 and no substantial film 16 will be formed, and the ion chamber 10 need not be activated. Should one wish to use the apparatus predominantly as an ion pump, then condensing coils 6 need not be activated, and condensing coil should be cooled to condense all the vapor passing through conduit 4, and only a liquid film 16 will exist in chamber 5. Then, the ionized gas produced in ion chamber 10 will be embedded in the continually flowing film 16 to be pumped out by the forepump. This unique control feature allows one to use the same physical apparatus to obtain the different pump actions.

As mentioned heretofore, the advantages of using a combination of both types of pumping action, is to overcome the inherent limitations possessed by each pump alone. This apparatus increases the effect of the pumping of the diffusion pump in that the pumping action of the condensing vapor is increased by the ionic current which increases the pumping rate of this system to make the speed not dependent on pump size. Unlike the ionic pump there is no poisoning of the cathode and little or no depletion with operation, thus permitting large volumes of gas to be pumped continuously. Accordingly, the film of the pumping fluid captures the molecules by embedment, and the target presented to the ionized molecules is constantly cleaned which eliminates the special problem associated with rare gases. Entrapment by condensing pumpmg fluid vapor and returning pumping fluid vapor from the discharged space also increases the pumping speed of the system. The optimum operating point of the apparatus may be selected by experimentation with the particular gas can be evacuated, so that the particular advantage otfered by this invention may best fit the need of the user.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention, as set forth in the objects thereof and in the accompanying claims.

I claim:

1. Vacuum pump apparatus comprising:

rneans for converting a pumping fluid to a vapor;

means connecting said converting means to a condensing chamber;

selective cooling means adapted to said connecting means for selectively condensing said vapor in order to form a film of said pumping fluid on one wall of said condensing chamber; and

an ionic chamber connected to a system to be evacuated to ionize the gas molecules from said system, and said ionic chamber further connected to said condensing chamber to transfer said ionized molecules into said condensing chamber, whereby some of said ionized gas molecules from said ionizing chamber are entrapped by said vapor and other of said molecules are embedded in said film on said one wall.

2. Vacuum pump apparatus comprising:

container means for holding a reservoir of pumping fluids;

means for heating said pumping fluid to produce a vapor;

a condensing chamber;

means connecting said container means to said condensing chamber to carry said vapor;

a first cooling means connected to said connecting means for selectively condensing said vapor in said connecting means in order to form a film of said pumping fluid on one wall of said condensing chamber;

an ionic chamber connected to a system to be evacuated to ionize the gas molecules from said system, and to be further connected to said condensing chamber to transfer said ionized molecules into said condensing chamber;

a second cooling means connected to said condensing chamber, whereby some of said ionized gas molecules from said ionizing chamber are entrapped by said vapor and said vapor is condensed by said second cooling means, and other of said molecules being embedded in said film on said one wall; and

outlet means in said condensing chamber adapted to be connected to a forepump to pump out said entrapped and embedded gas molecules.

3. Apparatus according to claim 2 including additional connecting means, connecting the condensed fluid in said condensing chamber to said reservoir in said container means for recirculating in said apparatus.

4. Apparatus according to claim 2 wherein said ionic chamber comprises:

an anode;

a source of ions; and

an auxiliary cathode being positioned to focus and accelerate said ionized gas molecules into said condensing chamber.

5. Apparatus according to claim 4 in which a magnet is positioned at said ionic chamber to cause said ions to move in a circular pattern to facilitate the ionization of said gas molecules prior to acceleration into said condensing chamber.

6. Apparatus according to claim 5 wherein a primary cathode is located on said one wall of said condensing chamber, said primary cathode being positioned to receive the focussed ionized gas molecules, such that said molecules become embedded in said film flowing over said primary cathode.

7. Method of producing a vacuum which comprises the steps of:

heating a pumping fluid to produce a vapor;

transferring said vapor to a condensing chamber;

partially condensing said vapor during transfer to form a film of said pumping fluid in said condensing chamber;

ionizing gas molecules to be evacuated;

injecting said ionized molecules into said condensing chamber;

entrapplng some of said ionized molecules by said vapor in said condensing chamber;

embedding other of said molecules in said film;

condensing said entrapping vapor in said condensing chamber; and

pumping out said entrapped and embedded ionized gas molecules.

8. Method according to claim 7 including the steps of removing the collected pumping fluid from said condensing chamber, and returning said fluid to a heating container to be recirculated.

9. Method according to claim 7 further including the step of passing a cooling fluid in indirect heat exchange to partially condense said vapor during transfer to said condensing chamber.

10. Method according to claim 7 further including the step of passing a cooling fluid in indirect heat exchange to condense said entrapping vapor in said condensing chamber.

References Cited UNITED STATES PATENTS 2,246,327 6/1941 Slepian 230101 3,053,436 9/1962 Sedlacsik 230-401 ROBERT M. WALKER, Primary Examiner. 

